HOW TO BUILD A SLURRY WALL

ONE OF THE MOST COMPLICATED CONSTRUCTION SECTIONS OF THE SAN FRANCISCO PORTION OF THE BAY AREA RAPID TRANSIT SYSTEM IS ALONG MARKET STREET, THE CITY'S MAIN ARTERY. CONTRACTS CALL FOR CONSTRUCTION OF DEEP, MASSIVE COFFERDAM WALLS WITHIN WHICH CUT-AND-COVER STATION CONSTRUCTION WILL FOLLOW. WORKING ENTIRELY FROM STREET LEVEL, IN TIGHT QUARTERS, THE CONTRACTOR MUST: (1) DRILL SLURRY-FILLED HOLES FOR INSTALLATION OF 405 STEEL SOLDIER PILES 5 FT, 10 IN. APART, (2) EXCAVATE OF SLURRY-FILLED SLOTS BETWEEN PILES, AND (3) FILL SLOTS WITH TREMIE-PLACED CONCRETE. THE FIRST STEP IS TO SET SEVERAL LAYERS OF TIMBER MATS ASTRIDE THE CENTER LINE OF A WALL SECTION TO PROVIDE A LEVEL WORKING AREA FOR A CRANE. SLURRY IS PREPARED NEARBY IN IN-SITE MIXING TANKS. POWDERED BAROID BENTONITE IN BAGS IS ADDED TO WATER IN MEASURED QUANTITIES TO PRODUCE A STABLE SUSPENSION WITH A DENSITY OF 65-70 LB. PER CU. FOOT. SLURRY IS CONTAINED AND CONTROLLED AND TESTED REGULARLY AS TO PROPER WEIGHT, VISCOSITY, WATER LOSS AND SAND CONTENT. A BATTERY OF DIESEL-POWERED VACSEAL PUMPS CIRCULATES SLURRY FROM TANKS THROUGH 2 AND 3-IN. RUBBER HOSE TO THE SLURRY TRENCH, THEN BACK TO OTHER TANKS FOR CLEANING AND FILTERING. WITHIN 24 HOURS AFTER A SERIES OF HOLES IS DRILLED, STEEL SOLDIER PILES MUST BE INSTALLED. DEPENDING ON WIDTH OF PILE AND SOIL CONDITIONS, DEPTH OF DRIVING WILL VARY. SOME PILES CAN BE DRIVEN WITH THE VIBRO-DRIVER TO FULL DEPTH AND OTHERS REQUIRE HEAVY PERCUSSION BLOWS OF A LARGE DIESEL HAMMER. AFTER EACH PILE IS INSTALLED, THE HOLE IS FILLED WITH CRUSHED STONE TO ASSURE SOIL STABILITY. WHEN A LINE OF PILES IS INSTALLED, THE NEXT STEP IS TO EXCAVATE ALL SOIL IN "SLOTS" BETWEEN PILE FLANGES. A HYDRAULICALLY OPERATED BUCKET WAS DEVELOPED THAT QUICKLY AND ACCURATELY GRABS A 1 1/2-YD BITE, EVEN AT DEPTHS OF 100 FEET. THE RIG CONSISTS OF A PIPE WITHIN A PIPE. THE INNERPIPE SERVES AS A RAM WHICH OPENS AND CLOSES THE BUCKET. WHEN A SLOT IS COMPLETELY EXCAVATED, A SOLDIER PILE HALF WAY BETWEEN THE TWO DRIVEN PILES, IS INSTALLED, RESULTING IN A FINAL PILE SPACING. THE DOUBLE SLOT MUST THEN BE FILLED WITH TREMIE-PLACED CONCRETE. A FRAME IS USED THAT STRADDLES THE SLOTS WITH TWO TREMIE PIPES, ONE FOR EACH SLOT, SUSPENDED FROM THE FRAME.

  • Supplemental Notes:
    • Vol 45, No 4, PP 64-65, 78, 4 PHOT
  • Publication Date: 1970-4

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  • Accession Number: 00215270
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Jun 15 1970 12:00AM